The objective of this proposal is to establish a T-cell culture line with specific killer activity. It is proposed that this can be achieved by hybridizing an induced killer cell with an in vitro cultured cell (T-cell lymphoma); the basic assumption is that among the synkaryons formed some will retain the desired properties of both parental cells (specific killer activity; continued proliferation in vitro), and these special hybrids can be selected and grown in vitro, ad infinitum.